JP2011248082A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of removing foreign matters adhered to the surface of contact type charging means without using a complex constitution.SOLUTION: An image forming apparatus 1 comprises a photoreceptor drum 2, a charging roller 3, a developing unit 5, a transfer roller 17, and a cleaning device 9. After performing a toner adhesion step for cleaning by reversely rotating the photoreceptor drum 2 to thrust-move the charging roller 3 and applying a first reverse bias to the charging roller 3, an aging step is performed by positively rotating the photoreceptor drum 2 to rub the surface of the charging roller 3 with cleaning toner. After the aging step, a cleaning toner recovery step is performed by positively rotating the photosensitive drum 2 and applying a charging bias to the charging roller 3, and thereby the surface of the charging roller 3 is cleaned.

Description

  The present invention relates to an image forming apparatus using an electrophotographic method, and more particularly to cleaning of a charger for charging a photosensitive member.

  Conventionally, in an image forming apparatus using an electrophotographic process, a charger (charging unit) is used to charge the surface of an image carrier (photosensitive member). As a charger, a corotron (or scorotron) charger that is disposed in non-contact with the photoconductor and charges the surface of the photoconductor by corona discharge, and is arranged in contact with or non-contact with the photoconductor to charge the photoconductor. A contact-type charger such as a charging roller is known. However, in recent years, in order to reduce the amount of ozone that is harmful to the human body, a charging roller having a smaller amount of ozone has been increasingly employed.

  When such a contact-type charger is used, if the surface of the photoreceptor, which is an image carrier, is contaminated with foreign matters such as toner components or paper dust of transfer paper, these foreign matters may be applied to the surface of the charging roller, for example. It has moved (whitening phenomenon) and caused charging failure, and image quality was deteriorated due to charging failure. In order to prevent such contamination (foreign matter adhesion) of the charging roller, conventionally, the charging roller is cleaned (refreshed) by bringing a cleaning member such as a rotary or fixed brush or sponge into contact with the charging roller. It was done.

  In particular, when refreshing is performed by bringing a brush roller or the like into rotational contact with the charging roller, the charging roller surface is less damaged and can be refreshed effectively. For cleaning with a brush, a method of applying a bias to the brush to electrically remove foreign matter, or external additives attached to the surface of the charging roller without applying a bias is disturbed by the brush and reattached to the photosensitive drum. Thus, a method for removing foreign matters is used.

  However, it is difficult to effectively suppress the whitening phenomenon of the charging roller over a long period of time by simply physically rubbing with such a cleaning member, and the whitening phenomenon of the charging roller occurs over time due to deterioration of the cleaning member. .

  Therefore, for example, Patent Document 1 discloses a new component by cleaning the contact charging member by allowing the toner electrostatically attached to the latent image carrier (image carrier) to pass through the contact charging member. A method is disclosed that makes it possible to easily reduce the amount of toner and external additives adhering to the contact charging member without increasing the number of toner. Further, Patent Document 1 discloses that a DC voltage on which an alternating current is superimposed is applied to the contact charging member while the toner on the image carrier is in contact with the contact charging member.

Japanese Patent Application Laid-Open No. 2002-196569

  In the method of Patent Document 1, by applying a direct current bias in which alternating current is superimposed on a charging member, the toner on the image carrier is an alternating current component of the bias and reciprocates in a minute gap between the image carrier and the charging member. The charging member is cleaned on the principle of attracting dirt such as an external additive attached to the charging member electrostatically or physically to the image carrier side.

  However, in such a removing method, the dirt on the charging member can be removed by electrostatically attracting the toner together with the toner to the image carrier side, but the dirt fixed with a certain level of force cannot be removed. Therefore, it has been difficult to effectively suppress the whitening phenomenon of the charging member as described above over a long period of time.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of removing foreign matter adhering to the surface of a contact-type charging unit without using a complicated configuration.

  To achieve the above object, the present invention provides an image carrier that can rotate in a predetermined rotation direction during image formation and forms an electrostatic latent image, a drive unit that rotates the image carrier, and the image carrier. Contact-type charging means for charging while rotating in contact with the body; first bias applying means capable of applying a charging bias to the charging means; and supplying toner to the surface of the image carrier to supply the surface of the image carrier A developing unit that uses the electrostatic latent image formed on the toner as a toner image, a transfer unit that transfers the toner image developed by the developing unit to a recording medium, and a transfer bias having a polarity opposite to that of the toner is applied to the transfer unit. A second bias applying unit capable of cleaning, and a cleaning unit disposed upstream of the charging unit and downstream of the transfer unit with respect to the rotation direction and capable of collecting toner remaining on the surface of the image carrier. Image forming equipment In the image forming apparatus, a rubbing unit capable of rubbing on the surface of the charging unit is provided, and cleaning toner is supplied from the developing device to the surface of the rotating image carrier during non-image formation, and the charging is performed from the surface of the image carrier. After the cleaning toner adheres substantially uniformly to the surface of the means, a linear velocity difference is provided between the rubbing means and the charging means, and the surface of the charging means is rubbed with the cleaning toner, After the surface of the charging unit is rubbed, the cleaning toner is moved from the surface of the charging unit to the surface of the image carrier, and the cleaning toner is collected from the surface of the image carrier to the cleaning unit. It is characterized by cleaning the surface of the charging means.

  According to the present invention, in the image forming apparatus configured as described above, a first reverse bias having a reverse polarity to the charging bias is applied to the charging unit when the toner is attached and when the charging unit is rubbed. It is characterized by that.

  According to the present invention, in the image forming apparatus having the above configuration, when the charging unit is rubbed, the charging unit between the charging unit and the rubbing unit at a contact portion between the charging unit and the rubbing unit. A linear speed difference is provided in the rotational direction or the axial direction.

  According to the present invention, in the image forming apparatus configured as described above, the rubbing means is the image carrier.

  According to the present invention, in the image forming apparatus configured as described above, when the charging unit is rubbed, a linear velocity of the charging unit is larger than a linear velocity of the image carrier.

  According to the present invention, in the image forming apparatus configured as described above, when the charging unit is rubbed, the charging unit reciprocates in the axial direction with respect to the image carrier.

  According to the present invention, in the image forming apparatus configured as described above, when the charging unit is rubbed, a linear velocity in the rotation direction of the charging unit is larger than a linear velocity in the rotation direction of the image carrier. .

  According to the present invention, in the image forming apparatus having the above configuration, the rubbing unit is a rubbing member that rotates in contact with the charging unit, and a bias having the same potential as that of the charging unit is applied to the rubbing member. It is characterized by that.

  According to the present invention, in the image forming apparatus having the above-described configuration, the rubbing member rotates following the charging unit at least during image formation, and a linear velocity between the charging unit and the charging unit during rubbing of the charging unit. It is characterized by a difference.

  According to the present invention, in the image forming apparatus having the above-described configuration, the linear velocity of the rubbing member is larger than the linear velocity of the charging device when the charging device is rubbed.

  According to the present invention, in the image forming apparatus configured as described above, the linear velocity in the rotation direction of the rubbing member is greater than the linear velocity in the rotation direction of the charging device when the charging device is rubbed. .

  According to the present invention, in the image forming apparatus configured as described above, when the charging unit is rubbed, the rubbing member reciprocates in the axial direction with respect to the charging unit.

  In the image forming apparatus having the above-described configuration, the first bias applying unit applies the charging bias to the charging unit when the cleaning toner is collected.

  According to the present invention, in the image forming apparatus having the above configuration, the driving unit rotates the image carrier in a direction opposite to the rotation direction when the cleaning toner is attached, When the cleaning toner is collected, the cleaning toner is rotated in the rotation direction.

  According to the present invention, in the image forming apparatus configured as described above, an interval between the developing unit and the charging unit on the surface of the image carrier is equal to or greater than a circumferential length of the charging unit.

  According to the present invention, in the image forming apparatus configured as described above, when the surface of the charging unit is cleaned, the second bias applying unit applies a second reverse bias having a polarity opposite to the transfer bias to the transfer unit. It is characterized by doing.

  According to the present invention, in the image forming apparatus having the above configuration, when the cleaning toner is attached, the linear velocity of the image carrier is lower than that during the image formation.

  According to the first configuration of the present invention, a rubbing unit capable of rubbing the charging unit is provided, and cleaning toner is supplied from the developing device to the rotating image carrier surface during non-image formation. After the cleaning toner adheres substantially uniformly from the surface of the carrier to the surface of the charging unit, a linear speed difference is provided between the rubbing unit and the charging unit, and the surface of the charging unit is slid by the cleaning toner. After rubbing the surface of the charging unit, the cleaning toner is moved from the surface of the charging unit to the surface of the image carrier, and the cleaning toner is collected from the surface of the image carrier to the cleaning unit. It is possible to remove foreign matter adhering to the surface of the contact-type charging means without using a complicated configuration.

  Further, according to the second configuration of the present invention, in the image forming apparatus having the first configuration, the first charging unit has a polarity opposite to the charging bias when the toner is attached to the charging unit and the charging unit is rubbed. By applying the reverse bias, the cleaning toner supplied to the image carrier can be more reliably attached to the charging unit and the foreign matter attached to the charging unit can be scraped off.

  According to the third configuration of the present invention, in the image forming apparatus having the first or second configuration, when the charging unit is rubbed, the charging unit is in contact with the charging unit at the contact portion between the charging unit and the rubbing unit. By providing a linear speed difference in the rotation direction or axial direction of the charging means with respect to the means, the scraping performance of the foreign matter adhering to the charging means with the cleaning toner is improved, so that the cleaning is reliably performed with a simpler configuration. Foreign matter can be attached to the toner, and the foreign matter attached to the charging means can be removed.

  According to the fourth configuration of the present invention, in the image forming apparatus having the third configuration, the rubbing means is an image carrier, so that a simpler configuration and no complicated members are added. The foreign matter adhering to the charging means can be removed.

  According to the fifth configuration of the present invention, in the image forming apparatus having the fourth configuration, when the charging unit is rubbed, the linear velocity of the charging unit is made larger than the linear velocity of the image carrier. In addition, the scraping performance of the foreign matter adhering to the charging means with the cleaning toner is improved. In addition, since the time required for rubbing can be shortened, the cleaning time of the charging means can be shortened.

  According to the sixth configuration of the present invention, in the image forming apparatus having the fifth configuration, when the rubbing unit is rubbed, the charging unit reciprocates in the axial direction with respect to the image carrier. Since the cleaning toner can scrape off the foreign matter from a direction different from the rotation direction, the foreign matter can be more reliably attached to the cleaning toner and the foreign matter attached to the charging unit can be removed.

  According to the seventh configuration of the invention, in the image forming apparatus having the fifth configuration, when the charging unit is rubbed, the linear velocity in the rotation direction of the charging unit is set to the linear velocity in the rotation direction of the image carrier. By making it larger than this, it is not necessary to add a complicated member for changing the linear velocity of the charging means, so that a simpler configuration can be achieved.

  According to the eighth configuration of the invention, in the image forming apparatus of the third configuration, the rubbing unit is a rubbing member that rotates in contact with the charging unit, and the rubbing member has the same potential as the charging unit. By applying this bias, it is possible to prevent the cleaning toner adhering to the charging means from moving to the rubbing member when cleaning the charging means, so that the foreign matter adhering to the charging means is scraped by the cleaning toner. And the recovery performance of the cleaning toner is also improved.

  According to the ninth configuration of the present invention, in the image forming apparatus having the above-described eighth configuration, the rubbing member rotates following at least the charging unit during image formation and is charged during the rubbing of the charging unit. By providing a linear velocity difference with the means, it is possible to further avoid the influence on image formation and to efficiently remove foreign matters attached to the charging means.

  According to the tenth configuration of the present invention, in the image forming apparatus having the ninth configuration, when the charging unit is rubbed, the linear velocity of the rubbing member is made larger than the linear velocity of the charging unit. The foreign matter adhering to the charging means can be removed without changing the linear velocity of the charging means.

  According to the eleventh configuration of the present invention, in the image forming apparatus having the tenth configuration, when the charging unit is rubbed, the linear velocity in the rotation direction of the rubbing member is set in the rotation direction of the charging unit. By making it larger than the linear velocity, it is not necessary to add a complicated member for changing the linear velocity of the rubbing member, so that a simpler configuration can be achieved.

  According to the twelfth configuration of the present invention, in the image forming apparatus having the tenth configuration, when the charging unit is rubbed, the rubbing member reciprocates in the axial direction with respect to the charging unit. Since the cleaning toner can rub off foreign matter from a direction different from the rotational direction and the axial direction, the foreign matter can be more reliably attached to the cleaning toner and the foreign matter attached to the charging means can be removed.

  According to the thirteenth configuration of the present invention, in the image forming apparatus having any one of the first to twelfth configurations, when the cleaning toner is collected, the first bias applying unit charges the charging unit. By applying the bias, the cleaning toner can be moved from the charging unit surface to the image carrier surface more efficiently and reliably.

  According to the fourteenth configuration of the present invention, in the image forming apparatus having any one of the first to thirteenth configurations, the rotation direction when the driving unit applies the cleaning toner to the image carrier. By rotating in the opposite direction and rotating in the rotation direction when collecting the cleaning toner, it is possible to avoid the cleaning toner from passing through the transfer means and the cleaning means when the cleaning toner adheres. The cleaning toner can be more reliably adhered to the surface. In addition, when the cleaning toner is collected, the cleaning toner can be collected more reliably by the cleaning means. Thus, the cleaning toner can be more reliably attached and collected.

  According to the fifteenth configuration of the present invention, in the image forming apparatus having any one of the first to fourteenth configurations, the interval between the developing unit and the charging unit on the surface of the image carrier is set to the circumferential length of the charging unit. By doing so, the cleaning toner sufficient to adhere to the surface of the charging unit can be supplied from the developing unit to the surface of the image carrier before reaching the surface of the charging unit. It becomes possible to make it adhere reliably.

  According to the sixteenth configuration of the present invention, in the image forming apparatus having any one of the first to fifteenth configurations, when the surface of the charging unit is cleaned, the second bias applying unit is transferred to the transfer unit. By applying a second reverse bias having a polarity opposite to that of the bias, the cleaning toner can be prevented from adhering to the transfer means, so that the cleaning toner can be more reliably attached and collected, and the toner image can be recorded. It is possible to avoid the occurrence of problems during transfer to the medium.

  According to the seventeenth configuration of the present invention, in the image forming apparatus having any one of the first to sixteenth configurations, when the cleaning toner is attached, the linear velocity of the image carrier is set higher than that at the time of image formation. Also, the cleaning toner can be more reliably attached from the surface of the image carrier to the surface of the charging unit.

1 is a schematic diagram showing an overall configuration of an image forming apparatus according to a first embodiment of the present invention. Schematic enlarged sectional view around the charging roller used in the image forming apparatus of the present embodiment Schematic perspective view showing the periphery of a first slide pulley and a first guide member used in the image forming apparatus according to the present embodiment. FIG. 4A is a diagram illustrating a state in which the charging roller is thrust-moved, and FIG. 4A is a diagram illustrating a state in which the charging roller is thrust-moved to one side, and FIG. Figure FIG. 5A is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the toner attaching process, and FIG. 5A is a diagram illustrating a state in which toner is supplied from the developing roller to the surface of the photosensitive drum. FIG. 5B is a diagram illustrating a state where toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 5C is a diagram illustrating a state where toner adheres substantially uniformly to the charging roller. The figure which shows rotation of the photosensitive drum in a aging process, a charging roller, and a developing roller FIG. 7A is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the toner collecting process, and FIG. 7A is a diagram illustrating a state in which the cleaning toner moves from the charging roller to the surface of the photosensitive drum; FIG. 7B is a diagram illustrating a state where the cleaning toner moves with the rotation of the photosensitive drum, and FIG. 7C is a diagram illustrating a state where the cleaning toner is collected by the cleaning device. 1 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to an embodiment. 10 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment. Timing chart of control procedure of FIG. FIG. 6 is a diagram illustrating a configuration around a charging roller used in an image forming apparatus according to a second embodiment of the present invention. FIG. 12A is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the cleaning toner attaching step, and FIG. 12A illustrates a state in which the cleaning toner is supplied from the developing roller to the surface of the photosensitive drum. FIG. 12B is a diagram showing a state where toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 12C is a diagram showing a state where toner adheres substantially uniformly to the charging roller. The figure which shows rotation of the photosensitive drum in a aging process, a charging roller, and a developing roller FIG. 14A is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the cleaning toner collecting step, and FIG. 14A is a diagram illustrating a state in which the cleaning toner moves from the charging roller to the surface of the photosensitive drum. FIG. 14B is a diagram showing a state in which the cleaning toner moves with the rotation of the photosensitive drum, and FIG. 14C is a diagram showing a state in which the cleaning toner is collected by the cleaning device. 1 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to an embodiment. 10 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment. Timing chart of control procedure of FIG. Schematic enlarged sectional view around a charging roller used in an image forming apparatus according to a third embodiment of the present invention. Schematic side view showing bearing member sides used in the image forming apparatus according to the present embodiment FIG. 20A is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner adhering step. FIG. 20A illustrates the cleaning toner supplied from the developing roller to the surface of the photosensitive drum. FIG. 20B is a diagram showing a state where toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 20C is a diagram where toner adheres substantially uniformly to the charging roller. Diagram showing state The figure which shows rotation of the photoconductive drum, a charging roller, a rubbing roller, and a developing roller in an aging process FIG. 22A is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner collecting step, and FIG. 22A illustrates a state in which the cleaning toner moves from the charging roller to the surface of the photosensitive drum. FIG. 22B is a diagram illustrating a state in which the cleaning toner moves as the photosensitive drum rotates, and FIG. 22C illustrates a state in which the cleaning toner is collected by the cleaning device. Figure showing 1 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to an embodiment. 10 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment. It is a timing chart of the control procedure of FIG. Schematic enlarged sectional view around a charging roller used in an image forming apparatus according to a fourth embodiment of the present invention. Schematic perspective view showing the periphery of a second slide pulley and a second guide member used in the image forming apparatus according to the present embodiment. FIG. 28A is a diagram showing a state in which the rubbing roller is in a thrust movement state, FIG. 28A is a diagram showing a state in which the charging roller is in a thrust movement in one side, and FIG. Illustration FIG. 29A is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner adhering step, and FIG. 29A illustrates the cleaning toner supplied from the developing roller to the surface of the photosensitive drum. FIG. 29B is a diagram showing a state where toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 29C is a diagram where toner adheres substantially uniformly to the charging roller. Diagram showing state The figure which shows rotation of the charging roller, the rubbing roller and the developing roller in the aging process FIG. 31A is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner collecting step, and FIG. 31A illustrates a state in which the cleaning toner moves from the charging roller to the surface of the photosensitive drum. FIG. 31B is a diagram illustrating a state in which the cleaning toner moves as the photosensitive drum rotates, and FIG. 31C illustrates a state in which the cleaning toner is collected by the cleaning device. Figure showing 1 is a block diagram illustrating an example of a control mechanism of an image forming apparatus according to an embodiment. 10 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment. 33 is a timing chart of the control procedure of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an image forming apparatus according to the first embodiment of the present invention. An image forming unit P is disposed in the image forming apparatus 1. The image forming unit P forms a predetermined image through each process of charging, exposure, development, and transfer.

  In this image forming portion P, a photosensitive drum (image carrier) 2 that carries a visible image (toner image) is disposed, and the toner image formed on the photosensitive drum 2 is a sheet (recording). The image is transferred onto a medium 6 and further fixed on the sheet 6 in the fixing unit 7 and then discharged from the apparatus main body. An image forming process for the photosensitive drum 2 is performed while the photosensitive drum 2 is rotated clockwise (predetermined rotational direction) in FIG. 1 by the first drive motor 21 (driving means, see FIG. 4). The

  Next, the image forming unit P will be described in detail. Around and around the photosensitive drum 2 rotatably disposed, a charging roller (charging means) 3 for charging the photosensitive drum 2, an exposure unit 4 for exposing image information to the photosensitive drum 2, and a photosensitive member A developing unit (developing unit) 5 that forms a toner image on the body drum 2, a cleaning device (cleaning unit) 9 that collects the developer (toner) remaining on the photosensitive drum 2, and an electrostatic latent image is removed. A static eliminator 10 is provided.

  First, the surface of the photosensitive drum 2 is uniformly charged by the charging roller 3 and then irradiated by the exposure unit 4 to form an electrostatic latent image corresponding to the image signal on the photosensitive drum 2. The developing unit 5 includes a developing roller 5 a disposed so as to face the photosensitive drum 2, and the developing unit 5 is filled with a predetermined amount of a magnetically charged positive component toner by a toner container 11. The toner is supplied to the surface of the photosensitive drum 2 by a developing roller 5a to which a developing bias is applied by a developing bias applying device (not shown), and is formed by exposure from the exposure unit 4 by electrostatic adhesion. A toner image corresponding to the electrostatic latent image is formed.

  The sheet 6 onto which the toner image is transferred is accommodated in a plurality of paper feed cassettes 12a, 12b, and 12c that accommodate the sheet 6, and a stack bypass (manual feed tray) 12d provided above the paper feed cassettes 12a, 12b, and 12c. The toner image is conveyed toward the photosensitive drum 2 on which the toner image is formed via the registration roller 14.

  At this time, the image writing signal is turned on, and the image is formed on the photosensitive drum 2 so that the toner image is transferred to a predetermined position on the sheet 6. A toner image on the photosensitive drum 2 is transferred onto the sheet 6 by applying an electric field at a lower portion of the photosensitive drum 2 by a transfer roller (transfer means) 17 to which a predetermined transfer bias is applied.

  The sheet 6 on which the toner image is transferred is conveyed to the fixing unit 7. In addition, the photosensitive drum 2 after the toner image is transferred is collected by the cleaning device 9 in preparation for the subsequent formation of a new electrostatic latent image. The sheet 6 conveyed to the fixing unit 7 is heated and pressed by the fixing roller 7a, and the toner image is fixed on the surface of the sheet 6 to form a predetermined image. The sheet 6 on which the image is formed is then discharged to a discharge tray 19 by a discharge roller 18.

  FIG. 2 is a schematic enlarged cross-sectional view around the charging roller used in the image forming apparatus of the present embodiment. In FIG. 2, the direction of the straight arrow indicates the conveyance direction of the sheet 6. Portions common to those in FIG. 1 are denoted by common reference numerals and description thereof is omitted. As the photosensitive drum 2, for example, an amorphous silicon (a-Si) drum can be used. Further, the photosensitive drum 2 is connected to the first drive motor 21 (see FIG. 4) via a drive gear (not shown) so as to rotate in the forward and reverse directions. In the drawing, it rotates (forward rotation) clockwise (forward rotation direction).

Above the photosensitive drum 2, a charging roller 3 that is rotatably in contact with the drum surface and charges the drum surface is disposed. In the charging roller 3, for example, a rubber layer (elastic layer) made of epichlorohydrin rubber having a resistance value of 10 ⁵ to 10 ⁶ Ω and a surface roughness R _Z = 10 μm is formed on the peripheral surface of a metal shaft (core metal) 3a. A solid type such as a conductive rubber roller can be suitably used, but is not particularly limited thereto. In addition, for example, a sponge type in which a foam rubber roller is covered with a tube can be used.

  The charging roller 3 is rotatably supported by the apparatus main body. The charging roller 3 is in pressure contact with the photosensitive drum 2 with a predetermined nip pressure, and is rotated by being driven by the photosensitive drum 2. Further, a positive charging bias is applied to the charging roller 3 during image formation.

  Specifically, the core metal 3 a of the charging roller 3 is electrically connected to a first power source (first bias applying device) 25, and a direct current in which an AC voltage is superimposed on the charging roller 3 from the first power source 25. A charging bias consisting of a voltage is applied. By applying such a charging bias, the surface of the photosensitive drum 2 can be charged by a current flowing according to the resistance of the rubber layer of the charging roller 3. Note that a DC voltage can be applied to the charging roller 3 from the first power supply 25. Here, the charging bias was set to DC voltage Vdc = 650V, AC voltage Vpp superimposed on the DC voltage = 1.2 kV, and frequency Vf = 1.5 kHz. The operation of the charging roller 3 when cleaning the charging roller 3 will be described later.

  The core 17a of the transfer roller 17 is electrically connected to a second power source (second bias applying device) 27, and has a polarity opposite to that of toner from the second power source 27 to the transfer roller 17 during image formation. A negative transfer bias is applied. Further, when cleaning the charging roller 3 to be described later, a positive polarity bias (reverse bias) having a polarity opposite to the transfer bias is applied to the transfer roller 17.

  The cleaning device 9 includes a cleaning blade 22 for removing residual toner on the surface of the photosensitive drum 2 and a cleaning roller for removing residual toner on the surface of the photosensitive drum 2 and rubbing and polishing the surface of the photosensitive drum 2. 23 and a recovery screw 24 as a toner discharging means are provided. The cleaning blade 22 is in contact with the surface of the photosensitive drum 2 so as to serve as a counter with respect to the normal rotation direction of the drum (clockwise in FIG. 2). The thickness of the cleaning blade 22 can be set to, for example, 1.2 mm depending on the apparatus configuration and the like.

  Residual toner and external additives on the surface of the photosensitive drum 2 are removed by the cleaning blade 22 and discharged from the toner discharge port (not shown) to the outside of the cleaning device 9 by the cleaning roller 23 and the collection screw 24. Although not shown, the cleaning device 9 is also provided with a scraper for setting the toner on the surface of the cleaning roller 23 to a predetermined layer thickness, a urethane seal for preventing waste toner in the cleaning device 9 from leaking to the outside, and the like. ing.

  By providing such a cleaning device 9, most of the residual toner and external additives are removed by the cleaning blade 22 as described above, but there are also foreign substances such as toner and external additives that pass through the cleaning blade 22 without being removed. Exists. Among the foreign matters that pass through the cleaning blade 22 and move to the downstream side in the forward rotation direction while adhering to the surface of the photosensitive drum 2, those having a polarity opposite to that of the toner adhere to the surface of the charging roller 3 due to the charging bias.

  If such foreign matter adheres to the charging roller 3, the potential of the surface of the charged roller 3 is different from that of the other portions, which may cause charging failure. As a result, black dots or the like appear on the formed image, and there is a possibility that an image defect may occur.

  Therefore, in this embodiment, in order to remove the foreign matter that causes the charging failure and the image failure, cleaning toner is supplied from the developing unit 5 to the surface of the rotating photosensitive drum 2 at the time of non-image formation, and the photosensitive member. After the cleaning toner adheres substantially uniformly from the surface of the drum 2 to the surface of the charging roller 3, a linear speed difference is provided between the photosensitive drum 2 and the charging roller, and the surface of the charging roller 3 is rubbed by the cleaning toner. After the surface of the charging roller 3 is rubbed, the cleaning toner is moved from the surface of the charging roller 3 to the surface of the photosensitive drum 2 to collect the cleaning toner from the surface of the photosensitive drum 2 to the cleaning device 9. The surface of the charging roller 3 was cleaned. The cleaning toner is not particularly limited as long as it is attached to the surface of the charging roller 3 and foreign matter can be attached thereto, but a toner used for image formation may be used.

  FIG. 3 is a schematic perspective view showing the periphery of the first slide pulley and the first guide member used in the image forming apparatus according to the present embodiment, and FIG. 4A shows a state in which the charging roller is thrust moved to one side. FIG. 4B is a diagram showing a state in which the thrust is moved to the other side. In the present embodiment, the charging roller 3 is configured to reciprocate in the axial direction (left-right direction) as it rotates (thrust movement).

  Specifically, as shown in FIG. 3, the right end portion of the shaft 3 a of the charging roller 3 is not shown in the figure, but slides in the axial direction (left-right direction in the figure) on a housing (not shown) that supports the charging roller 3. Supported as possible. On the other hand, a first slide pulley 51 is attached to the left side of the charging roller 3. The housing is provided with a first guide member 53 for guiding the first slide pulley 51.

  The first slide pulley 51 has a disc shape, and is attached to the left end portion of the shaft 3 a in a state inclined with respect to a plane orthogonal to the axial direction of the charging roller 3. Further, on both the left and right sides of the first slide pulley 51, ring-shaped first concave grooves 51a are provided so as to form thin portions between the bottom surfaces thereof. The first guide member 53 has a first guide groove 53a extending in the front-rear direction in which the lower portion of the first slide pulley 51 can be fitted. On both left and right side surfaces of the first guide groove 53a, first protrusions 53b that can be engaged with the first concave groove 51a of the first slide pulley 51 are provided.

  Then, the first protrusion 53b engages with the first groove 51a, so that the thin portion between the bottom surfaces of the first groove 51a of the first slide pulley 51 is seen from both axial sides of the first slide pulley 51. The first guide member 53 is slidably held by the first protrusion 53b. For this reason, when the charging roller 3 rotates and the rightmost portion of the thin portion of the first slide pulley 51 is sandwiched between the first protrusions 53b as shown in FIG. 4 moves to the left, and when the leftmost portion of the thin portion of the first slide pulley 51 is sandwiched between the first protrusions 53b as shown in FIG. 4B, the charging roller 3 moves to the right. Moving.

  That is, when the charging roller 3 rotates once, the charging roller 3 reciprocates once in the axial direction. Note that the inclination angle of the first slide pulley 51 is set so that the reciprocating distance of the charging roller 3 is ± 0.5 mm, that is, the amplitude of the charging roller 3 is 1 mm. Here, when the reciprocating distance of the charging roller 3 is greater than ± 5 mm, it is necessary to increase the lateral width of the apparatus main body, or it may be difficult to collect the cleaning toner on the left and right sides of the charging roller 3. . Therefore, for example, considering such a viewpoint, the reciprocating distance of the charging roller 3 is preferably ± 5 mm or less.

  Here, when the photosensitive drum 2 and the charging roller 3 rotate during image formation and non-image formation, the charging roller 3 is driven to rotate by the photosensitive drum 3 and moves in the thrust direction. Even if the charging roller 3 is thrust moving during image formation, the photosensitive drum 2 can be charged, and a large image defect does not occur.

  FIG. 5 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the toner attaching step (cleaning toner attaching step). FIG. 5A illustrates the toner from the developing roller to the surface of the photosensitive drum. FIG. 5B is a diagram illustrating a state in which toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 5C is a diagram in which toner is substantially uniform on the charging roller. It is a figure which shows the state adhering to. FIG. 6 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the aging process.

  FIG. 7 is a diagram showing the rotation of the photosensitive drum, the charging roller, and the developing roller in the toner collecting process (cleaning toner collecting process). FIG. 7A shows the cleaning toner exposed from the charging roller. FIG. 7B is a diagram illustrating a state in which the cleaning toner moves with the rotation of the photosensitive drum, and FIG. 7C is a diagram illustrating the state in which the cleaning toner moves. It is a figure which shows the state collect | recovered by the cleaning apparatus. 5 to 7, the cleaning toner is indicated by a black circle.

  At the time of image formation, as shown in FIG. 2 described above, since the photosensitive drum 2 is rotating forward (clockwise in the figure), the developing toner supplied from the developing roller 5a goes to the transfer roller 17. Here, the photosensitive drum 2 is composed of an a-Si photosensitive drum having an outer diameter of 30 mm, the linear velocity at the time of image formation is set to 300 mm / sec, and the outer diameter of the charging roller 3 is set to 12 mm. Further, since cleaning of the charging roller 3 during image formation hinders image formation, it is performed during non-image formation.

  First, the process of attaching the cleaning toner to the charging roller 3 will be described. The cleaning toner adhering step includes supplying the cleaning toner to the surface of the photosensitive drum 2 and adhering the cleaning toner supplied to the surface of the photosensitive drum 2 to the charging roller 3.

  First, supply of cleaning toner to the surface of the photosensitive drum 2 will be described. At the time of non-image formation, cleaning toner is supplied from the developing unit 5 to the surface of the photosensitive drum 2 to form a solid toner image. During non-image formation, the application of the charging bias to the charging roller 3, the application of the developing bias to the developing roller 5a, the application of the transfer bias to the transfer roller 17, and the rotation of the photosensitive drum 2 are stopped.

  From this state, as shown in FIG. 5A, the photosensitive drum 2 is rotated in the reverse direction (counterclockwise in the drawing) from the time of image formation (charging), and almost simultaneously with the start of the reverse rotation, the developing roller 5a. A developing bias is applied to the charging roller 3, a first reverse bias having a reverse polarity (here, negative polarity) to the charging bias is applied to the charging roller 3, and a reverse polarity to the transfer bias (see FIG. 2) (see FIG. 2). Here, the second reverse bias (second reverse bias) that is positive polarity is applied.

  Among these, by applying a developing bias, a cleaning toner image consisting of a solid image is formed on the surface of the photosensitive drum 2 due to a potential difference between the photosensitive drum 2 and the developing roller 5a, and the cleaning toner is applied to the surface of the photosensitive drum 2. Can be supplied. The linear speed of the photosensitive drum 2 during reverse rotation was set to about 100 mm / sec. Further, the first reverse bias applied to the charging roller 3 was a DC voltage, which was approximately −500V.

  At this time, the cleaning toner corresponding to the entire axial direction of the surface of the charging roller 3 and the range of at least one round in the circumferential direction is supplied to the surface of the photosensitive drum 2 so that the surface of the charging roller 3 is cleaned almost entirely. The toner can be attached. Here, the cleaning toner corresponding to the entire area in the axial direction of the surface of the charging roller 3 and the range of one round in the circumferential direction is supplied.

  Further, the distance between the charging roller 3 and the developing unit 5 on the surface of the photosensitive drum 2 is set to be equal to or longer than the circumferential length of the charging roller 3. As a result, the cleaning toner can be carried on the surface of the photosensitive drum 2 over at least one round of the surface of the charging roller 3 until the cleaning toner supplied from the developing unit 5 reaches the charging roller 3. . However, the interval is not particularly limited as long as the cleaning toner can be adhered substantially uniformly to the entire surface of the charging roller 3.

  Further, the supply time of the cleaning toner is not particularly limited as long as the cleaning toner can be substantially uniformly attached to substantially the entire surface of the charging roller 3, and the charging roller 3 and the developing unit 5 described above are not limited. The time required for supplying at least one cleaning toner of the charging roller 3 to the charging roller 3 may be determined according to the interval of the toner and the density of the cleaning toner image. If the supply time is too long, the cleaning toner adhering to the charging roller 3 becomes excessive, and there is a possibility that the cleaning toner not adhering to the charging roller 3 increases or the standby time is extended. Accordingly, for example, the supply time can be appropriately set in consideration of such a viewpoint.

  Here, since the second reverse bias (for example, 500 V) is applied to the transfer roller 17, the cleaning toner can reach the charging roller 3 without attaching the cleaning toner to the transfer roller 17. Further, the second reverse bias is applied to the transfer roller 17 from the start of reverse rotation of the photosensitive drum 2 (start of the cleaning toner attaching step) to the end of normal rotation (end of the cleaning toner collecting step). . Accordingly, it is possible to prevent the cleaning toner from adhering to the transfer roller 17 from the adhesion of the cleaning toner to the collection.

  The cleaning toner supplied from the developing roller 5 a to the surface of the photosensitive drum 2 when the photosensitive drum 2 rotates in the reverse direction does not go to the transfer roller 17, but the toner collected by the cleaning device 9 reaches the transfer roller 17. May adhere. Therefore, it is effective to apply the second reverse bias to the transfer roller 17 even during the reverse rotation.

  When the supply of the cleaning toner to the photosensitive drum 2 is finished, the application of the developing bias to the developing roller 5a is stopped. On the other hand, the application of the second reverse bias to the transfer roller 17 is continued.

  Next, the adhesion of the cleaning toner to the surface of the charging roller 3 will be described. As shown in FIG. 5B, the reverse rotation of the photosensitive drum 2 is continued even after the supply of the cleaning toner from the developing roller 5a is stopped, and the first reverse bias is applied to the charging roller 3. It was decided to continue. When the reverse rotation of the photosensitive drum 2 is continued, the cleaning toner supplied to the surface of the photosensitive drum 2 reaches the nip between the photosensitive drum 2 and the charging roller 3.

  When the cleaning toner enters the nip between the charging roller 3 and the photosensitive drum 2, the physical action due to the nip pressure and the electrical action due to the potential difference between the photosensitive drum 2 and the charging roller 3. As a result, the toner moves from the photosensitive drum 2 to the surface of the charging roller 3. Thereby, the cleaning toner on the surface of the photosensitive drum 2 can be physically attached to the surface of the charging roller 3.

  As a result, as shown in FIG. 5C, the cleaning toner adheres substantially uniformly to the entire surface of the charging roller 3. Further, since the linear velocity of the photosensitive drum 2 is set to about 100 mm / sec after the supply of the cleaning toner, the cleaning toner can be more reliably attached to the charging roller 3.

  Further, since the first reverse bias applied to the charging roller 3 is a DC voltage of about −500 V following the supply of the cleaning toner described above, the cleaning toner can be more reliably attached to the charging roller 3. The cleaning toner can be attached to the charging roller 3 by rotating the photosensitive drum 2 in the reverse direction without applying the charging bias and the first reverse bias to the charging roller 3.

  Here, the first reverse bias is applied to the charging roller 3 from the start of the reverse rotation of the photosensitive drum 2, but the cleaning toner supplied onto the photosensitive drum 2 arrives at the charging roller 3. The first reverse bias can be applied.

  The attachment time of the cleaning toner from the photosensitive drum 2 to the charging roller 3 is not particularly limited as long as the cleaning toner can be attached substantially uniformly to the surface of the charging roller 3, and at least the charging roller 3. What is necessary is just to make it the time required for one round. If the adhesion time is short, the cleaning toner adhered to the surface of the charging roller 3 may not be sufficiently uniformed, and foreign matter may not be sufficiently adhered to the cleaning toner.

  On the other hand, when the adhesion time becomes longer, the cleaning toner adheres firmly to the surface of the charging roller 3, and the cleaning toner is moved from the surface of the charging roller 3 to the surface of the photosensitive drum 2 when collecting the cleaning toner described later. May be difficult. It also leads to longer waiting times. Therefore, for example, taking this viewpoint into consideration, the adhesion time can be set as appropriate.

  Here, in the cleaning toner adhering step, the linear speed at the time of reverse rotation of the photosensitive drum 2 is set to about 100 mm / sec, which is about 1/3 at the time of image formation. The cleaning toner can be more reliably adhered to the surface. However, the linear velocity at the time of reverse rotation may be that the cleaning toner is supplied from the developing unit 5 to the surface of the photosensitive drum 2 and the cleaning toner is adhered substantially uniformly from the surface of the photosensitive drum 2 to the surface of the charging roller 3. If possible, it is not particularly limited, and can be set as appropriate according to the state of adhesion of the cleaning toner to the surface of the charging roller 3.

  Next, the rubbing (aging) process on the surface of the charging roller 3 will be described. When the foreign matter adhering to the charging roller 3 on the surface of the charging roller 3 comes into contact with the cleaning toner, the foreign matter adheres to the cleaning toner. In this state, as shown in FIG. 6, the rotation direction of the photosensitive drum 2 is switched to rotate forward.

  Further, the linear speed of the positive rotation of the photosensitive drum 2 was returned to about 300 mm / sec. As a result, the number of times each surface of the charging roller 3 comes into contact with the photosensitive drum 2 is increased, so that the foreign material scraping performance by the cleaning toner is improved. Further, the first reverse bias is continuously applied to the charging roller 3. Accordingly, it is possible to prevent the cleaning toner attached to the surface of the charging roller 3 from returning from the charging roller 3 to the photosensitive drum 2. Further, as described above, since the charging roller 3 is in the thrust movement, the linear velocity of the charging roller 3 is larger than that of the photosensitive drum 2 in the axial direction.

  Note that the linear velocity of the photosensitive drum 2 at the time of aging is not particularly limited as described later, as long as the cleaning toner can scrape foreign matter on the surface of the charging roller 3, and the movement of the cleaning toner is not limited. It can be set as appropriate according to the situation and the recovery situation.

  Due to the difference in the linear velocity in the axial direction, it is possible to improve the scraping performance of foreign matters by the cleaning toner. Further, when the charging roller 3 is moved in a thrust manner, the cleaning toner can scrape the foreign matter from a direction different from the rotation direction, so that the foreign matter can be more reliably attached to the toner. The pressure contact force of the charging roller 3 with respect to the photosensitive drum 2 is set to such an extent that the surface of the photosensitive drum 2 is shaved and does not affect image formation during the aging process.

  The aging time can be, for example, 10 seconds from the start of normal rotation of the photosensitive drum 2. During this 10 seconds, the photosensitive drum 2 having an outer diameter of 30 mm rotates about 32 times and the charging roller 3 having an outer diameter of 12 mm rotates about 80 times, so that the surface of the charging roller 3 is sufficiently rubbed with a cleaning toner. Can be done.

  The aging time can be appropriately set according to the state of scraping of foreign matters by the cleaning toner on the surface of the charging roller 3, and is not particularly limited. However, if the aging time is shortened, there is a possibility that the foreign matter cannot be scraped off sufficiently. If the aging time is long, the standby time may be unnecessarily prolonged. Therefore, for example, considering this viewpoint, the aging time can be set as appropriate.

  In addition, when the photosensitive drum 2 is switched from reverse rotation to forward rotation, if a bias (both charging bias and first reverse bias) is applied to the charging roller 3 at the moment when the photosensitive drum 2 stops, the photosensitive drum Leakage with respect to the drum 2 occurs, and a current flows intensively at one place on the photosensitive drum 2, which may cause a pinhole on the surface of the photosensitive drum 2. Therefore, it is preferable to stop the bias application to the charging roller 3 when the rotation direction of the photosensitive drum 2 is switched.

  Next, a cleaning toner collecting step will be described. After performing the aging process, as shown in FIG. 7A, the photosensitive drum 2 is continuously rotated in the forward direction, and at the same time, a charging bias is applied to the charging roller 3. Further, the linear velocity of the photosensitive drum 2 was set to 300 mm / sec, and the application of the second reverse bias to the transfer roller 17 was continued.

  As a result, due to the potential difference between the charging roller 3 and the photosensitive drum 2, the cleaning toner attached to the surface of the charging roller 3 moves to the photosensitive drum 2. As the cleaning toner moves, foreign matter attached to the cleaning toner also moves to the photosensitive drum 2.

  When the photosensitive drum 2 continues to rotate forward, the cleaning toner that has moved to the surface of the photosensitive drum 2 passes through the developing unit 5 as shown in FIG. 7B, and as shown in FIG. 7C. Passes through the transfer roller 17. At this time, since the second reverse bias is applied to the transfer roller 17, the cleaning toner that has passed through the developing unit 5 passes through the developing roller 5 without adhering to the transfer roller 17 (see FIG. 2). And collected by the cleaning device 9. The collection time can be set to 5 seconds from the start of the cleaning toner collection process, for example.

  During this 5 seconds, the photosensitive drum 2 having an outer diameter of 30 mm rotates about 16 times and the charging roller 3 having an outer diameter of 12 mm rotates about 40 times, so that the cleaning toner is sufficiently applied from the charging roller 3 to the surface of the photosensitive drum 2. Further, the cleaning toner moved to the surface of the photosensitive drum 2 by the cleaning device 9 can be sufficiently collected.

  The collection time can be set as appropriate according to the collection status of the cleaning toner from the surface of the photosensitive drum 2, and is not particularly limited. However, if the collection time is shortened, the cleaning toner may not be sufficiently collected. If the collection time is long, the photosensitive drum 2 is rotated even after the collection is sufficiently collected, and the standby time may be unnecessarily prolonged. There is. Therefore, for example, taking this viewpoint into consideration, the collection time can be set as appropriate.

  Further, since the linear velocity of the photosensitive drum 2 is set to 300 mm / sec, which is the same as that during image formation, during the positive rotation of the photosensitive drum 2 in the collection of cleaning toner, the cleaning toner can be efficiently collected. . However, the linear velocity of the photosensitive drum 2 at the time of recovery is particularly limited as long as the cleaning toner is moved from the surface of the charging roller 3 to the surface of the photosensitive drum 2 and the cleaning toner can be recovered by the cleaning device 9. However, it can be set as appropriate according to the movement status and recovery status of the cleaning toner.

  Then, after the cleaning toner collecting step is completed, the application of the charging bias to the charging roller 3, the application of the reverse bias to the transfer roller 17, and the normal rotation of the photosensitive drum 2 are stopped.

  Next, a method for controlling the cleaning of the surface of the charging roller 3 will be described. FIG. 8 is a block diagram illustrating an example of a control mechanism of the image forming apparatus according to the present embodiment. Portions common to FIGS. 1 to 7 are denoted by the same reference numerals and description thereof is omitted. The image forming apparatus 1 includes an image forming unit P, a fixing unit 7, a cleaning device 9, a first drive motor 21, a first power source 25, a second power source 27, an image input unit 32, an AD conversion unit 33, a storage unit 34, and a control. The unit 35 and the operation panel 36 are included.

  When the image forming apparatus 1 is a copying machine, the image input unit 32 includes a scanning optical system equipped with a scanner lamp that illuminates the document during copying and a mirror that changes the optical path of reflected light from the document, and reflected light from the document. The image forming apparatus 1 is a printer. The image forming apparatus 1 includes a condenser lens that collects and forms an image and a CCD that converts the imaged image light into an electrical signal. In this case, the reception unit receives image data transmitted from a personal computer or the like. The image signal input from the image input unit 32 is sent to the control unit 35, appropriately performs image processing such as gradation processing, and after being converted into a digital signal by the AD conversion unit 33, an image in the storage unit 34 to be described later. It is sent to the memory 40.

  The image forming unit P is composed of the photosensitive drum 2, the charging roller 3, the exposure unit 4, the developing unit 5, the transfer roller 17, and the like. Then, an electrostatic latent image is formed on the photosensitive drum 2. In addition to the photosensitive drum 2, the transfer roller 17, the cleaning roller 23 in the cleaning device 9, the conveying screw 24 (see FIG. 2), and the like are also rotationally driven by the first drive motor 21 via gears and clutches (not shown). The control unit 35 transmits a control signal to the first drive motor 21 to control the rotation and stop of the photosensitive drum 2, the transfer roller 17, the cleaning roller 23, and the recovery screw 24.

  The storage unit 34 includes an image memory 40, a RAM 41, and a ROM 42. The image memory 40 stores an image signal (data) input by the image input unit 32 and digitally converted by the AD conversion unit 33, and is controlled. Send to unit 35. The RAM 41 and ROM 42 store an image processing program, processing contents, and the like of the control unit 35. Further, a program for controlling the reverse rotation and forward rotation timing and linear velocity of the photosensitive drum 2, a developing bias for supplying cleaning toner from the developing unit 5 to the surface of the photosensitive drum 2, and application and application thereof. The stop timing, the charging bias applied to the charging roller 3, the first reverse bias, the application and application stop timing thereof, the second reverse bias applied to the transfer roller 17, the application and application stop timing, and the like are also stored.

  The control unit 35 is, for example, a central processing unit (CPU), and generally controls the image input unit 32, the image forming unit P, the cleaning device 9 and the like according to a set program and is input from the image input unit 32. The image signal is converted into image data (print data) by scaling processing or gradation processing as necessary. The exposure unit 4 irradiates a laser beam based on the processed image data to form an electrostatic latent image on the surface of the photosensitive drum 2. Further, the control unit 35 also controls each part of the image forming apparatus such as the image input unit 32, the charging roller 3, the exposure unit 4, and the developing unit 5 in accordance with the set program.

  Further, when the cleaning mode of the surface of the charging roller 3 is set during non-image formation, the control unit 35 reversely rotates the photosensitive drum 2 and applies a first reverse bias to the charging roller 3 so that the developing unit 5 performs photosensitive. A function of supplying cleaning toner to the surface of the photosensitive drum 2 and attaching the cleaning toner supplied to the surface of the photosensitive drum 2 to the surface of the charging roller 3 (performing the cleaning toner attaching step) or after the cleaning toner attaching step The function of performing the aging process by rotating the photosensitive drum 2 forward, and the photosensitive drum 2 after the aging process by rotating the photosensitive drum 2 forward and applying the charging bias to the charging roller 3 to the surface of the photosensitive drum 2 The cleaning toner is moved to the surface and collected by the cleaning device 9 (the cleaning toner collecting process is performed), and the recovery process is performed from the cleaning toner attaching process. Until also has a function of applying a second reverse bias to the transfer roller 17.

  When the image forming apparatus 1 is a copying machine, the operation panel 36 includes an operation unit including a plurality of operation keys and a display unit (none of which is shown) for displaying setting conditions, the state of the apparatus, and the like. In addition to setting the print size and other printing conditions by the user, for example, when the image forming apparatus 1 has a facsimile function, the facsimile transmission destination is registered in the storage unit 34, and the registered transmission destination is read out. It is also used for various settings such as rewriting and rewriting. The operation panel 36 includes a display unit displayed on a personal computer (not shown) when the image forming apparatus 1 is a printer.

  The cleaning mode can be automatically set after the predetermined number of prints have been completed or one print job has been completed, in addition to the user setting the operation panel 36. Further, the timing is not particularly limited, and can be appropriately set according to the contamination state of the surface of the charging roller 3.

  Next, an example of control of the image forming apparatus according to the present embodiment will be described. FIG. 9 is a flowchart showing an example of a control procedure of the image forming apparatus according to the present embodiment, and FIG. 10 is a timing chart of the control procedure of FIG. With reference to FIG. 8 and FIG. 10, this control example will be described according to the steps of FIG.

  First, after completion of image formation (printing), application of a charging bias to the charging roller 3, operation of the developing unit, application of a bias to the transfer roller 17, and rotation of the photosensitive drum 2 are stopped (OFF).

  When the cleaning mode is set (start) during the non-image formation, the control unit 35 reversely rotates the photosensitive drum 2 by rotating the first drive motor 21 in reverse, and the charging roller 3 is moved to the photosensitive drum 2. Immediately after the rotation and the thrust movement, the first reverse bias is applied to the charging roller 3, the second reverse bias is applied to the transfer roller 17, and the development bias is applied to the developing roller 5a. The cleaning toner is supplied to the surface 2, and the cleaning toner is attached from the photosensitive drum 2 to the charging roller 3 (step S1).

  Next, when cleaning toner for one rotation of the charging roller 3 is supplied to the surface of the photosensitive drum 2, the control unit 35 stops applying the developing bias to the developing roller 5a and supplies the cleaning toner. Stop (step S2). Next, for example, after 2 seconds have elapsed from the start of reverse rotation of the photosensitive drum 2, the control unit 35 switches the rotation direction of the first drive motor 21, rotates the photosensitive drum 2 forward, and performs an aging process (step). S3). As a result, the foreign matter adheres to the cleaning toner while being scraped off by the cleaning toner on the surface of the charging roller 3.

  Here, after completion of the cleaning toner attaching process in step S2, and before the aging process in step S3, the application of the developing bias to the developing roller 5a is stopped and the first reverse bias is applied to the charging roller 3. Then, after the application of the second reverse bias to the transfer roller 17 was stopped, the reverse rotation of the photosensitive drum 2 was once stopped.

  Next, for example, 10 seconds after the start of normal rotation of the photosensitive drum 2, the control unit 35 rotates the photosensitive drum 2 in the normal direction and switches the bias applied to the charging roller 3 to apply the charging bias ( Step S4). As a result, the cleaning toner to which foreign matter is attached moves from the surface of the charging roller 3 to the surface of the photosensitive drum 2 that rotates forward. Further, the cleaning toner moved to the surface of the photosensitive drum 2 passes through the transfer roller 17 to which the second reverse bias is applied without being attached, and is collected by the cleaning device 9.

  Here, after application of the first reverse bias to the charging roller 3 and application of the second reverse bias to the transfer roller 17 are stopped after the aging process in step S3 and before the cleaning toner is collected in step S4, Once, the positive rotation of the photosensitive drum 2 was stopped.

  For example, after 5 seconds from the start of the cleaning toner collecting process, the control unit 35 applies the charging bias to the charging roller 3, the second reverse bias to the transfer roller 17, and the forward rotation of the photosensitive drum 2. After stopping (step S5), the process ends. Here, after the application of the charging bias to the charging roller 3 and the application of the second reverse bias to the transfer roller 17 were stopped, the forward rotation of the photosensitive drum 2 was stopped.

  As described above, the photosensitive drum 2 that can be rubbed with the charging roller 3 is provided during non-image formation, and cleaning toner is supplied from the developing unit 5 to the surface of the rotating photosensitive drum 2 during non-image formation. After the cleaning toner adheres substantially uniformly from the surface of the drum 2 to the surface of the charging roller 3, a linear speed difference is provided between the surface of the drum 2 and the photosensitive drum 2, and the surface of the charging roller 3 is rubbed with the cleaning toner. After rubbing the surface of the charging roller 3, the cleaning toner is moved from the surface of the charging roller to the surface of the photosensitive drum 2 to collect the cleaning toner from the surface of the photosensitive drum 2 to the cleaning device 9. The surface was cleaned.

  As a result, the foreign matter adhering to the charging roller 3 can be efficiently removed by adhering to the cleaning toner, so that the foreign matter adhering to the surface of the contact-type charging roller 3 can be removed without using a complicated configuration. Is possible. Furthermore, stable image quality can be obtained over a long period of time.

  In the present embodiment, the charging roller 3 is thrust moved also in the cleaning toner attaching step and the cleaning toner collecting step. However, the charging roller 3 is thrust moved only when the charging roller 3 is rubbed. You can also. Accordingly, the cleaning toner can be easily attached to the charging roller 3 and can be easily moved from the charging roller 3 to the photosensitive drum 2.

  In this case, as an example, the shaft 3a of the charging roller 3 is rotatably supported, and one end in the axial direction of the shaft 3a is urged toward the other end by a compression spring or the like. The charging roller 3 can be thrust driven by enabling the other end of the shaft 3a to be pressed by a solenoid plunger provided in the apparatus main body and turning the solenoid on and off to cause the plunger to appear and retract. In addition, this makes it possible to prevent the charging roller 3 from undergoing thrust movement during image formation.

  In the present embodiment, since the first reverse bias is applied to the charging roller 3 during the cleaning toner attaching step and the aging step, the toner supplied to the photosensitive drum 2 is more reliably attached to the charging roller 3. At the same time, the foreign matter can be scraped off by the cleaning toner. Further, the linear velocity difference between the charging roller 3 and the photosensitive drum 2 is not particularly limited in the rotation direction, and a linear velocity difference can be provided in the axial direction.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described. FIG. 11 is a diagram showing a configuration around the charging roller used in the image forming apparatus according to the second embodiment of the present invention. FIG. 12 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the cleaning toner attaching process. FIG. 12A illustrates the cleaning toner supplied from the developing roller to the surface of the photosensitive drum. FIG. 12B is a diagram illustrating a state in which toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. 12C is a diagram in which the toner is substantially uniformly applied to the charging roller. It is a figure which shows the state which adhered.

  FIG. 13 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the aging process, and FIG. 14 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the cleaning toner collecting process. 14A is a diagram showing a state where the cleaning toner moves from the charging roller to the surface of the photosensitive drum, and FIG. 14B shows a state where the cleaning toner moves as the photosensitive drum rotates. FIG. 14C is a diagram illustrating a state in which the cleaning toner is collected by the cleaning device. In FIGS. 12 to 14, the cleaning toner is indicated by a black circle. Moreover, the same code | symbol is attached | subjected to the part which is common in FIGS. 1-10, and description is abbreviate | omitted.

  In the present embodiment, when the charging roller 3 is rubbed, a linear velocity in the rotational direction is provided instead of providing a linear linear velocity difference between the charging roller 3 and the photosensitive drum 2.

  As shown in FIG. 11, the shaft 3 a of the charging roller 3 is connected to a second drive motor 41 provided separately from the first drive motor 21 via a first clutch mechanism 43. In the aging process, when the first clutch mechanism 43 is operated and the shaft 3a is drivingly connected to the second drive motor 41, the driving force from the second drive motor 41 is transmitted, and the charging roller 3 is moved to the photosensitive drum. 2 is driven and rotated in the same direction as the photosensitive drum 2 at the contact portion. Since the other configuration is the same as that of the first embodiment, differences from the first embodiment will be mainly described below.

  In the present embodiment, the cleaning toner adhering step is performed in the same manner as in the first embodiment by stopping the driving of the charging roller 3 and rotating the charging roller 3 with the photosensitive drum 2 without thrust movement. It was decided. Thus, after the cleaning toner is supplied from the developing roller 5a to the surface of the photosensitive drum 2 as shown in FIG. 12A, the cleaning toner is supplied to the photosensitive drum 2 as shown in FIG. 12B. Then, the cleaning toner adheres substantially uniformly to the surface of the charging roller 3 as shown in FIG.

  Next, in the aging process, as shown in FIG. 13, the rotation direction of the photosensitive drum 2 is switched to rotate forward (clockwise in the drawing) at a linear speed of 300 mm / sec, and the charging roller 3 is moved to the second drive motor 41. To drive and rotate at a linear speed of 360 mm / sec. Further, a first reverse bias is applied to the charging roller 3 as in the first embodiment. As a result, the linear velocity of the charging roller 3 is greater than the linear velocity of the photosensitive drum 2, and the linear velocity difference between the charging roller 3 and the photosensitive drum 2 is 60 mm / sec.

  By providing the linear velocity difference in this way, the rub-off performance of foreign matters by the cleaning toner is improved during the aging process. Further, by making the linear velocity of the charging roller 3 higher than the linear velocity of the photosensitive drum 3, the time for rubbing the foreign matter by the cleaning toner on the surface of the charging roller 3 can be shortened.

  Note that the linear velocity of the photosensitive drum 2 can be made smaller than the linear velocity of the charging roller 3. However, as described above, if a bias is applied to the charging roller 3 while the photosensitive drum 2 is stopped, a pinhole may be generated on the surface of the photosensitive drum 2. Therefore, in consideration of such a viewpoint, it is preferable that the photosensitive drum 2 is at least rotating (linear speed is higher than 0), and the linear speed is more preferably 20 mm / sec or more, and further 100 mm / sec or more. preferable.

  Further, if the linear velocity of the photosensitive drum 2 is increased, the rubbing time can be shortened, but the work for returning to the setting at the time of image formation may be complicated. Considering this viewpoint, it is preferable that the linear velocity of the photosensitive drum 2 at the time of aging is the same as that at the time of image formation (for example, approximately 300 mm / sec).

  In the cleaning toner adhering step, the driving of the charging roller 3 is stopped, and the photosensitive drum 2 is rotated forward and charged as shown in FIG. 14A in the same manner as in the first embodiment described above. After applying a charging bias to the roller 3 and moving the cleaning toner adhering to the charging roller 3 to the photosensitive drum 2 as shown in FIG. 14B, as shown in FIG. The cleaning toner is collected by the cleaning device 9 (see FIG. 2).

  FIG. 15 is a block diagram illustrating an example of a control mechanism of the image forming apparatus according to the present embodiment. Portions common to those in FIG. 8 are denoted by common reference numerals and description thereof is omitted. As shown in FIG. 15, the storage unit 34 stores parameters related to the timing for operating and stopping the second drive motor 41.

  The control unit 35 reversely rotates the photosensitive drum 2 and applies the first reverse bias to the charging roller 3 and the developing bias to the developing roller 5a with the operation of the second drive motor 41 stopped, thereby cleaning toner. After the cleaning toner attaching process and the cleaning toner attaching process, the photosensitive drum 2 is rotated forward, the second drive motor 41 is operated, and the first reverse bias is applied to the charging roller 3 to perform the aging process. After the aging process, the photosensitive drum 2 is rotated forward to stop the operation of the second drive motor 41, and a charging bias is applied to the charging roller 3 to perform a cleaning toner collecting process. Yes.

  Next, an example of control of the image forming apparatus according to the present embodiment will be described. FIG. 16 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment, and FIG. 17 is a timing chart of the control procedure of FIG. Portions common to FIGS. 9 and 10 are denoted by common reference numerals and description thereof is omitted. With reference to FIG. 15 and FIG. 17, this control example will be described according to the steps of FIG.

  First, in a state in which the driving of the charging roller 3 is stopped, the charging roller 3 is driven and rotated with the photosensitive drum 2 without thrust movement, and steps S11 and S12 are performed in the same manner as steps S1 and S2 in the first embodiment. Execute the cleaning toner adhering step.

  Next, for example, after 2 seconds have elapsed from the start of reverse rotation of the photosensitive drum 2, the control unit 35 switches the rotation direction of the first drive motor 21 to rotate the photosensitive drum 2 in the forward direction, and the second drive motor 41 The charging roller 3 is rotated to perform an aging process (step S13). As a result, the foreign matter adheres to the cleaning toner while being scraped off by the cleaning toner on the surface of the charging roller 3.

  Next, for example, after 10 seconds have elapsed from the start of normal rotation of the photosensitive drum 2, the control unit 35 stops driving the charging roller 3 and causes the charging roller 3 to rotate following the photosensitive drum 2 so that the first embodiment described above. As in step S4, a cleaning toner collecting step is performed (step S14). As a result, the cleaning toner to which foreign matter adheres moves from the surface of the charging roller 3 to the surface of the photosensitive drum 2 that rotates forward, and the cleaning toner that has moved to the surface of the photosensitive drum 2 is applied with the second reverse bias. It passes through the transfer roller 17 without adhering to it and is collected by the cleaning device 9.

  For example, after 5 seconds from the start of the cleaning toner collecting step, the control unit 35 applies the charging bias to the charging roller 3, applies the second reverse bias to the transfer roller 17, and the like, as in the first embodiment. After the forward rotation of the photosensitive drum 2 is stopped (step S15), the process ends.

  In the present embodiment, as in the first embodiment, the rotation of the photosensitive drum 2 is performed between the cleaning toner attaching process and the aging process, and between the aging process and the cleaning toner collecting process. Was temporarily stopped.

  As described above, also in the present embodiment, since the linear speed difference is provided between the photosensitive drum 2 and the charging roller during the aging process, the foreign matter scraping performance by the cleaning toner when the charging roller 3 is rubbed. Will improve. Further, in the present embodiment, since the linear velocity difference is provided between the photosensitive drum 2 and the charging roller 3 in the rotation direction, it is possible to avoid adding a complicated member for providing such a linear velocity difference and cleaning. This improves the scraping performance of foreign matter by the toner for use. In this embodiment, since the linear speed of the charging roller 3 is made larger than the linear speed of the photosensitive drum 3, the rubbing time on the surface of the charging roller 3 can be shortened.

  Moreover, in this embodiment, although the 2nd drive motor 41 was provided, it can also be set as the structure which does not provide the 2nd drive motor 41 in addition. In such a case, for example, the shaft 3a of the charging roller 3 can be meshed with a gear connected to the first drive motor 21 by switching a clutch mechanism (not shown) during the aging process, and meshed with the gear. Sometimes, the gear ratio is adjusted so that the linear velocity of the charging roller 3 is larger than that of the photosensitive drum 2. Thereby, the linear velocity of the charging roller 3 can be varied without providing the second drive motor 41.

  In the first and second embodiments, when the charging roller 3 is rubbed, a linear speed difference is provided between the charging roller 3 and the photosensitive drum 2 to improve the scraping performance of foreign matters by the cleaning toner. However, the rubbing means of the present invention is not particularly limited to the photosensitive drum 2.

  Next, an image forming apparatus according to a third embodiment of the present invention will be described. FIG. 18 is a schematic enlarged cross-sectional view of the periphery of the charging roller used in the image forming apparatus according to the third embodiment of the present invention, and FIG. 19 shows the side of the bearing member used in the image forming apparatus according to the present embodiment. It is a schematic side view.

  FIG. 20 is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner attaching step. FIG. 20A illustrates the cleaning toner from the developing roller to the photosensitive member. FIG. 20B is a diagram illustrating a state where toner is attached to the charging roller from the surface of the photosensitive drum, and FIG. 20C is a diagram illustrating a state where toner is charged to the charging roller. It is a figure which shows the state adhere | attached substantially uniformly. FIG. 21 is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the aging process.

  FIG. 22 is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner collecting step. FIG. 22A illustrates the cleaning toner from the charging roller to the photosensitive member. FIG. 22B is a diagram illustrating a state in which the cleaning toner moves along with the rotation of the photosensitive drum, and FIG. 22C illustrates a state in which the cleaning toner is cleaned. It is a figure which shows the state collect | recovered by an apparatus. Portions common to FIGS. 1 to 17 are denoted by common reference numerals and description thereof is omitted.

  In the present embodiment, a rubbing roller (rubbing member, rubbing means) 55 that rotates in contact with the charging roller 3 is provided. The rubbing roller 55 is driven to rotate by the charging roller 3 during image formation, and the rubbing roller 55 is rubbed during the aging process. By driving and rotating the roller 55, a linear velocity difference is provided in the rotation direction between the rubbing roller 55 and the charging roller 3. In the present embodiment, the linear velocity of the rubbing roller 55 is made larger than the linear velocity of the charging roller.

As shown in FIG. 18, a rubbing roller 55 made of a conductive brush roller is disposed above the charging roller 3. The rubbing roller 55 is, for example, made of 6-nylon, a brush diameter of 12 mm, a filament thickness of 2 denier, a filament density of 40,000 filaments / cm ² , and a brush resistance value of 0.7 × around a support shaft 55a made of a cored bar. A 10 ⁷ Ω conductive fur brush is formed. The rubbing roller 55 is not particularly limited, and may be formed of a conductive sponge-based foam member. However, considering the life of the charging roller 3, it is preferably a brush roller. .

  As shown in FIG. 19, the support shaft 55 a of the rubbing roller 55 is rotatably supported by a conductive bearing member 57 together with the shaft 3 a of the charging roller 3. Specifically, the bearing member 57 is formed with two through holes 57a capable of supporting the support shaft 55a of the rubbing roller 55 and the shaft 3a of the charging roller 3, respectively. The support shaft 55a and the shaft 3a are supported. Further, the through holes 57 a are formed at intervals such that the rubbing roller 55 is pressed against the charging roller 3 with a pressing force that does not affect the charging of the charging roller 3.

  Accordingly, when the first reverse bias is applied to the charging roller 3 during the rubbing of the charging roller 3, the first reverse bias having the same potential is also applied to the rubbing roller 55. Further, one end of the support shaft 55a is connected to a third drive motor 61 that is independent of the first drive motor 21 via the second clutch mechanism 63 similar to that of the second embodiment. Since the other configuration is the same as that of the first embodiment, differences from the first embodiment will be mainly described below.

  In this embodiment, in the cleaning toner adhering step, the charging roller 3 is driven to rotate with the photosensitive drum 2 without thrust movement, and the driving of the rubbing roller 55 is stopped, which is the same as in the first embodiment described above. As shown in FIG. 20A, after the cleaning toner is supplied from the developing roller 5a to the surface of the photosensitive drum 2, the cleaning toner is supplied to the photosensitive drum 2 as shown in FIG. To the charging roller 3, and as shown in FIG. 20C, the cleaning toner adheres substantially uniformly to the surface of the charging roller 3.

  Next, in the aging process, as shown in FIG. 21, the rotation direction of the photosensitive drum 2 is switched, and is rotated forward (clockwise in the drawing) at a linear speed of 300 mm / sec, and the charging roller 3 is driven to rotate (linear speed). 300 mm / sec), and the rubbing roller 55 is driven and rotated by the third drive motor 61 at a linear speed of 360 mm / sec. Further, a first reverse bias is applied to the charging roller 3 as in the first embodiment. As a result, the linear velocity of the rubbing roller 55 is greater than the linear velocity of the charging roller 3, and the linear velocity difference between the rubbing roller 55 and the charging roller 3 is 60 mm / sec.

  By providing the linear velocity difference in this way, the rub-off performance of foreign matters by the cleaning toner is improved during the aging process. Further, by making the linear velocity of the rubbing roller 55 higher than the linear velocity of the photosensitive drum 3, the rubbing time on the surface of the charging roller 3 can be shortened.

  However, the linear velocity of the rubbing roller 55 can be made smaller than that of the charging roller 3. Further, by changing the linear speed of the charging roller 3 as shown in the second embodiment, the linear speed of the charging roller 3 can be made larger or smaller than that of the rubbing roller 55. However, as described above, if the bias of the charging roller 3 is applied while the photosensitive drum 2 is stopped, a pinhole may occur. Considering this viewpoint, it is preferable that the charging roller 3 is at least rotating (the linear velocity is larger than 0), and the linear velocity is more preferably 20 mm / sec or more, and further preferably 100 mm / sec or more.

  In addition, as described above, considering the viewpoint of shortening the rubbing time and the complexity of the work for returning to the setting at the time of image formation, the linear velocity of the charging roller 3 at the time of aging is set to the value at the time of image formation. It is preferable that the linear velocity is the same (for example, approximately 300 mm / sec).

  In this embodiment, since the charging roller 3 and the rubbing roller 55 are set to the same potential when the charging roller 3 is rubbed, the cleaning toner and foreign matter are prevented from moving from the charging roller 3 to the rubbing roller 55. can do.

  Then, in the cleaning toner collecting step, the drive of the rubbing roller 55 is stopped, and the photosensitive drum 2 is rotated forward as shown in FIG. 22A in the same manner as in the first embodiment described above. A charging bias is applied to the charging roller 3 to move the cleaning toner adhering to the charging roller 3 to the photosensitive drum 2 as shown in FIG. 22B, and then as shown in FIG. 22C. The cleaning toner is collected by the cleaning device 9 (see FIG. 2).

  It is to be noted that since the cleaning roller 55 is driven and rotated by the charging roller 3 to prevent the cleaning toner from staying between the charging roller 3 and the rubbing roller 55, the cleaning toner on the surface of the charging roller 3 is collected. Becomes easy.

  Further, as described above, since the rubbing roller 55 has the same potential as that of the charging roller 3, even when a charging bias is applied to the charging roller 3, the cleaning toner on the surface of the charging roller 3 moves to the rubbing roller 55. Can be prevented. Thereby, it becomes easy to collect the cleaning toner from the charging roller 3.

  In this case, since the charging roller 3 is driven to rotate during image formation, the rubbing roller 55 has almost no ability to clean the surface of the charging roller 3. However, the rubbing roller 55 may be configured to have a cleaning ability for the charging roller 3 during image formation.

  FIG. 23 is a block diagram illustrating an example of a control mechanism of the image forming apparatus according to the present embodiment. Portions common to those in FIG. 8 are denoted by common reference numerals and description thereof is omitted. As shown in FIG. 23, the storage unit 34 stores parameters relating to the timing at which the third drive motor 61 is activated and stopped.

  Further, the control unit 35 reversely rotates the photosensitive drum 2 and applies the first reverse bias to the charging roller 3 and the developing bias to the developing roller 5a with the operation of the third drive motor 61 stopped, thereby cleaning toner. After the cleaning toner attaching process and the cleaning toner attaching process, the photosensitive drum 2 is rotated forward, the third drive motor 61 is operated, and the first reverse bias is applied to the charging roller 3 to perform the aging process. After the aging process, the photosensitive drum 2 is rotated forward to stop the operation of the third drive motor 61, and the charging bias is applied to the charging roller 3 to perform the cleaning toner collecting process. Yes.

  Next, an example of control of the image forming apparatus according to the present embodiment will be described. FIG. 24 is a flowchart illustrating an example of a control procedure of the image forming apparatus according to the present embodiment, and FIG. 25 is a timing chart of the control procedure of FIG. Portions common to FIGS. 9 and 10 are denoted by common reference numerals and description thereof is omitted. With reference to FIGS. 23 and 25, this control example will be described in accordance with the steps in FIG.

  First, the charging roller 3 is driven to rotate with the photosensitive drum 2 without thrust movement, the drive of the rubbing roller 55 is stopped, and steps S21 and S22 are executed in the same manner as steps S1 and S2 in the first embodiment. Then, a cleaning toner adhesion process is performed. At this time, the rubbing roller 55 rotates following the charging roller 3.

  Next, for example, after 2 seconds have elapsed from the start of the reverse rotation of the photosensitive drum 2, the control unit 35 switches the rotation direction of the first drive motor 21 to rotate the photosensitive drum 2 in the forward direction, and the third drive motor 61 The rubbing roller 55 is rotated to perform an aging process (step S23). As a result, the foreign matter adheres to the cleaning toner while being scraped off by the cleaning toner on the surface of the charging roller 3.

  Next, for example, after 10 seconds have elapsed from the start of normal rotation of the photosensitive drum 2, the control unit 35 stops driving the rubbing roller 55 and causes the rubbing roller 55 to rotate following the charging roller 3. As in step S4 of step 1, a cleaning toner collecting step is performed (step S24). As a result, the cleaning toner to which foreign matter adheres moves from the surface of the charging roller 3 to the surface of the photosensitive drum 2 that rotates forward, and the cleaning toner that has moved to the surface of the photosensitive drum 2 is applied with the second reverse bias. It passes through the transfer roller 17 without adhering to it and is collected by the cleaning device 9.

  For example, after 5 seconds from the start of the cleaning toner collecting step, the control unit 35 applies the charging bias to the charging roller 3, applies the second reverse bias to the transfer roller 17, and the like, as in the first embodiment. After the forward rotation of the photosensitive drum 2 is stopped (step S25), the process ends.

  In the present embodiment, as in the first embodiment, the rotation of the photosensitive drum 2 is performed between the cleaning toner attaching process and the aging process, and between the aging process and the cleaning toner collecting process. Was temporarily stopped.

  As described above, also in this embodiment, during non-image formation, cleaning toner is supplied from the developing unit 5 to the surface of the rotating photosensitive drum 2, and the surface of the charging drum 3 is cleaned almost uniformly from the surface of the photosensitive drum 2. After the toner is attached, a linear velocity difference is provided between the rubbing roller 55 and the charging roller 3, and the surface of the charging roller 3 is rubbed with the cleaning toner. After the rubbing of the surface of the charging roller 3, The surface of the charging roller 3 can be cleaned by moving the cleaning toner from the surface of the charging roller 3 to the surface of the photosensitive drum 2 and collecting the cleaning toner from the surface of the photosensitive drum 2 to the cleaning device 9.

  In the present embodiment, since the bias having the same potential as that of the charging roller 3 is applied to the rubbing roller 55, the surface of all the charging rollers 3 during the cleaning toner attaching process, the aging process, and the cleaning toner collecting process is cleaned. At this time, it is possible to prevent the cleaning toner attached to the charging roller 3 from moving to the rubbing roller 55 or the photosensitive drum 2, so that the foreign matter attached to the charging roller 3 is scraped by the cleaning toner, and The collection performance of the cleaning toner is improved.

  In the present embodiment, the rubbing roller 55 rotates following at least the charging roller 3 at the time of image formation, and provides a linear speed difference with the rubbing roller 55 at the time of rubbing the charging roller 3. Therefore, it is possible to further avoid the influence on image formation and to efficiently remove the foreign matter adhering to the charging roller 3.

  In this embodiment, since the linear speed of the rubbing roller 55 is made larger than the linear speed of the charging roller 3 during the aging process, the foreign matter attached to the charging roller 3 can be removed without changing the linear speed of the charging roller 3. Can be removed. In the present embodiment, since the linear velocity of the rubbing roller 55 is larger than the linear velocity of the charging roller 3 in the rotation direction during the aging process, a complicated member for changing the linear velocity of the rubbing roller 55 is added. Therefore, a simpler configuration can be obtained.

  Note that the linear velocity difference between the rubbing roller 55 and the charging roller 3 is not particularly limited to being provided in the rotational direction, and may be provided in the axial direction.

  Next, an image forming apparatus according to a fourth embodiment of the present invention will be described. FIG. 26 is a schematic enlarged cross-sectional view of the periphery of the charging roller used in the image forming apparatus of this embodiment, and FIG. 27 is the vicinity of the second slide pulley and the second guide member used in the image forming apparatus according to this embodiment. FIG. 28 is a diagram showing a state in which the rubbing roller is in a thrust movement, and FIG. 28 (a) is a diagram showing a state in which the sliding roller is in a thrust movement in one direction. FIG. 28 (b) is a diagram showing a state in which the thrust is moved to the other side.

  FIG. 29 is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner attaching step. FIG. 29A illustrates the cleaning toner from the developing roller to the photosensitive member. FIG. 29B is a diagram showing a state in which toner is supplied to the surface of the drum, FIG. 29B is a diagram showing a state in which toner adheres to the charging roller from the surface of the photosensitive drum, and FIG. It is a figure which shows the state adhere | attached substantially uniformly. FIG. 30 is a diagram illustrating rotation of the photosensitive drum, the charging roller, and the developing roller in the aging process.

  FIG. 31 is a diagram illustrating rotation of the photosensitive drum, the charging roller, the rubbing roller, and the developing roller in the cleaning toner collecting step. FIG. 31A illustrates the cleaning toner from the charging roller to the photosensitive member. FIG. 31B is a diagram illustrating a state in which the cleaning toner moves along with the rotation of the photosensitive drum, and FIG. 31C illustrates a state in which the cleaning toner is cleaned. It is a figure which shows the state collect | recovered by an apparatus. Portions common to FIGS. 1 to 25 are denoted by common reference numerals and description thereof is omitted.

  In the present embodiment, as shown in FIGS. 26, 27 and 28, instead of connecting the support shaft 55a of the rubbing roller 55 to the third drive motor 61 shown in the third embodiment, the first embodiment described above is used. The rubbing roller 55 is moved in a thrust manner in the same manner as the charging roller 3 is moved in a thrust manner.

  Specifically, as shown in FIG. 27, the right end portion of the support shaft 55a of the rubbing roller 55 is not shown in the figure, but the housing (not shown) that supports the charging roller 3 and the rubbing roller 55 is axially ( It is supported so as to be slidable in the horizontal direction in the figure. On the other hand, a second slide pulley 71 similar to the first slide pulley 51 shown in the first embodiment is attached to the left side of the rubbing roller 55.

  Further, the housing is provided with a second guide member 73 for guiding the second slide pulley 71, which is the same as the first guide member 53 shown in the first embodiment. It has the 2nd guide groove 73a similar to the 1st guide groove 53a shown in one embodiment, and it is the same as that of the 1st projection 53b shown in a 1st embodiment in the right-and-left both sides side of this 2nd guide groove 73a. A second protrusion 73b is provided.

  The second protrusion 73b engages with the second concave groove 71a, so that the thin portion between the bottom surfaces of the second concave groove 71a of the second slide pulley 71 can be seen from both axial sides of the second slide pulley 71. The second protrusion 73b of the second guide member 73 is slidably held. Therefore, when the sliding roller 55 rotates and the rightmost portion of the thin portion of the second slide pulley 71 is sandwiched between the second protrusions 73b as shown in FIG. When the roller 55 moves to the left and the leftmost portion of the thin portion of the second slide pulley 71 is sandwiched between the second protrusions 73b as shown in FIG. Move to the right. That is, when the rubbing roller 55 makes one rotation, the rubbing roller 55 reciprocates once in the axial direction.

  As in the first embodiment, the inclination angle of the second slide pulley 71 is set such that the reciprocating distance of the rubbing roller 55 is ± 0.5 mm, that is, the amplitude of the rubbing roller 55 is 1 mm. The reciprocating distance of the rubbing roller 55 is preferably ± 5 mm or less.

  Here, when the photosensitive drum 2 and the charging roller 3 rotate during image formation and non-image formation, the rubbing roller 55 is driven to rotate by the charging roller 3 and moves in the thrust direction. However, as in the first embodiment, it is also possible to adopt a configuration in which thrust movement is performed only when the charging roller 3 is rubbed. Even if the rubbing roller 55 is thrust during image formation, the photosensitive drum 2 can be charged by the charging roller 3 and no image defect occurs. Since other configurations are the same as those of the third embodiment, differences from the third embodiment will be mainly described below.

  In the present embodiment, in the cleaning toner adhering step, the rubbing roller 55 is driven to rotate with the charging roller 3 while being moved in a thrust manner, as in the third embodiment described above, as shown in FIG. In addition, after the cleaning toner is supplied from the developing roller 5a to the surface of the photosensitive drum 2, the cleaning toner adheres to the charging roller 3 from the photosensitive drum 2 as shown in FIG. As shown in c), the cleaning toner adheres substantially uniformly to the surface of the charging roller 3.

  Next, in the aging process, the rotation direction of the photosensitive drum 2 is switched, and is rotated forward (clockwise in the drawing) at a linear speed of 300 mm / sec. Further, the first reverse bias is applied to the charging roller 3 as in the third embodiment. As a result, the photosensitive drum 2 and the charging roller 3 driven to rotate and the rubbing roller 55 that moves in a thrust manner are rubbed, and foreign matter on the surface of the charging roller 3 can be rubbed off by the cleaning toner.

  Then, in the cleaning toner collecting step, as in the third embodiment described above, the photosensitive drum 2 is rotated forward and a charging bias is applied to the charging roller 3 as shown in FIG. As shown in FIG. 31B, after the cleaning toner attached to the charging roller 3 is moved to the photosensitive drum 2, the cleaning toner is removed from the cleaning device 9 (FIG. 31C) as shown in FIG. 2).

  FIG. 32 is a block diagram illustrating an example of a control mechanism of the image forming apparatus according to the present embodiment. Portions common to those in FIG. 23 are denoted by common reference numerals and description thereof is omitted. The control unit 35 applies a first reverse bias to the charging roller 3 and a developing bias to the developing roller 5a while the photosensitive drum 2 is rotated in the reverse direction, and attaches the cleaning toner. After the process, the photosensitive drum 2 is rotated forward and a first reverse bias is applied to the charging roller 3 to perform the aging process. After the aging process, the photosensitive drum 2 is rotated forward and the charging roller 3 is rotated. It has a function of performing a cleaning toner collecting step by applying a charging bias.

  Next, an example of control of the image forming apparatus according to the present embodiment will be described. FIG. 33 is a flowchart showing an example of a control procedure of the image forming apparatus according to the present embodiment, and FIG. 34 is a timing chart of the control procedure of FIG. Portions common to FIGS. 24 and 25 are denoted by common reference numerals and description thereof is omitted. This control example will be described in accordance with the steps in FIG. 33 with reference to FIGS. 32 and 34.

  First, the charging roller 3 is driven to rotate with the photosensitive drum 2, and the rubbing roller 55 is driven to rotate with the charging roller 3 while being moved in a thrust manner. As in steps S21 and S22 of the third embodiment, Step S32 is executed to perform a cleaning toner attaching step.

  Next, for example, after 2 seconds have elapsed from the start of reverse rotation of the photosensitive drum 2, the control unit 35 switches the rotation direction of the first drive motor 21 to rotate the photosensitive drum 2 in the forward direction and performs an aging process (step) S33). As a result, the foreign matter adheres to the cleaning toner while being scraped off by the cleaning toner on the surface of the charging roller 3.

  Next, for example, after 10 seconds have elapsed from the start of normal rotation of the photosensitive drum 2, the control unit 35 rotates the photosensitive drum 2 in the normal direction, and similarly to step S24 of the third embodiment, the cleaning toner collecting step. Is performed (step S34). As a result, the cleaning toner to which foreign matter adheres moves from the surface of the charging roller 3 to the surface of the photosensitive drum 2 that rotates forward, and the cleaning toner that has moved to the surface of the photosensitive drum 2 is applied with the second reverse bias. It passes through the transfer roller 17 without adhering to it and is collected by the cleaning device 9.

  Then, for example, after 5 seconds from the start of the cleaning toner collecting step, the control unit 35 applies the charging bias to the charging roller 3, applies the second reverse bias to the transfer roller 17, and After the forward rotation of the photosensitive drum 2 is stopped (step S35), the process ends.

  In this embodiment, as in the third embodiment, the rotation of the photosensitive drum 2 is performed between the cleaning toner attaching process and the aging process and between the aging process and the cleaning toner collecting process. Was temporarily stopped.

  According to this embodiment, since the rubbing roller 55 reciprocates in the axial direction with respect to the charging roller 3 during the aging process, the cleaning toner can scrape foreign matter from a direction different from the rotation direction. Thus, it is possible to more reliably adhere the foreign matter to the cleaning toner and remove the foreign matter attached to the charging roller 3.

  Instead of the rubbing roller 55, a plate-like brush member can be used as the rubbing member. In this case, the rubbing member may be moved in a thrust manner as in the present embodiment.

  In each of the above embodiments, since the first power supply 25 applied a charging bias to the charging roller 3 during the cleaning toner collecting step, the cleaning toner can be moved more efficiently from the surface of the charging roller 3 to the surface of the photosensitive drum 2. And it can be performed reliably.

  By making the charging bias at the time of recovery the same as the charging bias at the time of image formation, the configuration can be prevented from becoming complicated. However, the charging bias at the time of collection is not particularly limited, and can be set as appropriate according to the movement state of the cleaning toner from the surface of the charging roller 3 to the surface of the photosensitive drum 2. Further, depending on the movement state of the cleaning toner, it is not always necessary to apply the charging bias at the time of collection.

  In each of the above embodiments, since the first drive motor 21 rotates the photosensitive drum 2 in the reverse direction when performing the cleaning toner attaching step and the aging step and in the forward direction when performing the cleaning toner collecting step, the cleaning toner is used. During the adhesion process and the aging process, the cleaning toner can be prevented from passing through the transfer roller 17 and the cleaning device 9. Thereby, the cleaning toner can be reliably attached to the surface of the charging roller 3 in a shorter time. In addition, the cleaning toner 9 can more reliably recover the cleaning toner during the cleaning toner recovery process. Therefore, the cleaning toner is more effectively attached and collected.

  Further, the transfer roller 17 and the cleaning device 9 are separated from the photosensitive drum 2 so that the cleaning toner does not adhere to the transfer roller 17 before being attached to the surface of the charging roller 3 or is not collected by the cleaning device 9. Therefore, it is not necessary to provide a separating device or the like, so that an increase in the size of the device and a complicated configuration of the device can be avoided.

  However, the cleaning drum can be attached to the charging roller 3 by rotating the photosensitive drum 2 forward. In such a case, it is possible to prevent the cleaning toner from adhering to the transfer roller 17 by rotating the photosensitive drum 2 forward and applying a second reverse bias to the transfer roller 17. Further, by separating the cleaning device 9 from the photosensitive drum 2 by the separation device as described above, it is possible to prevent the cleaning toner 9 from collecting the cleaning toner. In the cleaning toner collecting step, the cleaning device 9 may be brought into contact with the photosensitive drum 2.

  When the photosensitive drum 2 is rotated forward during the cleaning toner attaching step, the surface of the photosensitive drum 2 is charged by the charging roller 3 with the cleaning toner image, and then the electrostatic latent image formed of the solid image by the exposure unit 4 is used. It is also possible to form an image and supply the cleaning toner to the electrostatic latent image from the developing roller 5a. In this case, after charging, the application of the charging bias to the charging roller 3 may be stopped before the cleaning toner reaches the surface of the charging roller 3.

  In each of the above embodiments, when the surface of the charging roller 3 is cleaned, the second power source 27 applies a second reverse bias having a polarity opposite to the transfer bias to the transfer roller 17, so that the cleaning toner is applied to the transfer roller 17. It can prevent adhesion. This makes it possible to more reliably attach and collect the cleaning toner, and avoid problems associated with the transfer of the toner image to the recording medium. However, it is also possible to provide a separation device as described above and separate the transfer roller 17 from the photosensitive drum 2 instead of applying the second reverse bias. In the case where a non-contact type transfer member is used as the transfer means, it is not necessary to provide such a separation device.

  For example, when a tandem type image forming apparatus having an intermediate transfer belt is used, a separation device for separating the intermediate transfer belt from the photosensitive drum 2 is provided in order to prevent the cleaning toner from adhering to the intermediate transfer belt. be able to. In this embodiment, the second reverse bias is applied to the transfer roller 17 from the cleaning toner attaching process to the collecting process, but the second reverse bias is applied only during the forward rotation of the photosensitive drum 2. You can also.

  In each of the above-described embodiments, the distance between the charging roller 3 and the developing unit 5 on the surface of the photosensitive drum 2 is equal to or greater than the circumferential length of the charging roller 3. Cleaning toner for at least one rotation of the roller 3 can be supplied from the developing unit 5 to the surface of the photosensitive drum 2 before reaching the surface of the charging roller 3. As a result, the cleaning toner can be more reliably attached to the surface of the charging roller 3.

  In each of the above embodiments, when the cleaning toner is attached, the linear velocity of the photosensitive drum 2 is made smaller than that during image formation, and therefore the cleaning toner adheres from the surface of the photosensitive drum 2 to the surface of the charging roller 3. Can be performed more reliably. In particular, in this embodiment, since the linear velocity at this time is set to approximately 1/3 at the time of image formation, the cleaning toner can be more reliably attached to the surface of the charging roller 3.

  In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the material, outer diameter, linear velocity, and the like of the above-described photosensitive drum 2 and charging roller 3 are not particularly limited, and can be appropriately set according to the apparatus configuration and the like. In the above embodiment, the present invention is applied to a positively charged toner. However, the present invention can also be applied to a negatively charged toner. The charging bias and the transfer bias are changed to a positive polarity or negative polarity bias according to the polarity of the toner. You only have to set it.

  In this embodiment, since a one-component developer is used, toner supply (development) from the developing unit 5 to the photosensitive drum 2 at the time of image formation is performed even when the photosensitive drum 2 is rotated forward and backward during non-image formation. This is effective because it does not significantly affect the conditions. However, even when a two-component developer is used and the developer chain of the two-component developer comes into contact with the photosensitive drum 2 at the time of development, by appropriately setting development conditions and the like, the photosensitive drum 2 Can be reversely rotated to clean the charging roller 3 described above.

  In addition, a magnetic roller (toner supply member) in which a developer chain is formed in the development unit 5 using a two-component developer, and a development roller (toner carrier) to which only toner is supplied from the magnetic roller are provided for development. Even in the image forming apparatus that causes only the toner to fly from the roller to the photosensitive drum 2, the above-described charging roller 3 can be cleaned. Further, the present invention can be applied to various image forming apparatuses such as a digital multifunction peripheral, a tandem color copying machine, a copying machine such as an analog monochrome copying machine, or a facsimile or a laser printer.

  In the above embodiment, since the a-Si photosensitive drum is used as the photosensitive drum 2, the cleaning toner is applied by applying a DC voltage superimposed with an AC voltage to the charging roller 3 when the cleaning toner is collected. Becomes easier to move from the charging roller 3 to the photosensitive drum 2. However, an organic photoreceptor (OPC) drum can also be used. In such a case, a DC voltage can be applied as a charging bias to the charging roller 3 during image formation, and a DC voltage can be applied to the charging roller 3 also during the cleaning toner collecting step.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a present Example.

  As shown in FIGS. 1 to 4 and 8, the image forming apparatus 1 according to the first embodiment of the present invention is used to clean the charging roller 3 as shown in FIGS. However, after printing 100,000 images with a printing rate of 5%, the image quality was evaluated. The linear speed of the photosensitive drum 2 during image formation was set to 300 mm / sec. Further, in cleaning the charging roller 3, the linear speed during reverse rotation of the photosensitive drum 2 is set to 100 mmsec, the linear speed during forward rotation is set to 300 mm / sec, and the thrust movement width of the charging roller 3 is set to 1 mm (± 0.5 mm). ).

Evaluation of image quality was performed by printing a 25% half image of 600 dpi 1 × 1 dot and measuring density unevenness of the image. For the measurement of image unevenness, a transmission density measuring device (Model 310T) manufactured by X-rite was used, and when the image density (transmission density) unevenness ΔTD value was 0.1 or less, the image quality was good (circle mark). When the value exceeds 0.1, the image quality is judged as poor (x mark). The results are shown in Table 1.

  As shown in FIGS. 1, 11 and 15, the image forming apparatus 1 according to the second embodiment of the present invention is used, and the charging roller 3 is cleaned as shown in FIGS. However, after printing 100,000 images with a printing rate of 5%, the image quality was evaluated. The linear speed of the photosensitive drum 2 during image formation was set to 300 mm / sec. Further, when the charging roller 3 is cleaned, the linear speed during reverse rotation of the photosensitive drum 2 is 100 mmsec, the linear speed during forward rotation is 300 mm / sec, and the linear speed of the rubbing roller 55 during the aging process is 360 mm / sec. sec. Other than that was carried out similarly to Example 1, and measured the density unevenness of the image and evaluated image quality. The results are shown in Table 1.

Comparative example

In the image forming apparatus 1 shown in FIG. 1, image quality was evaluated after printing 100,000 images with a printing rate of 5% while bringing a brush roller made of a fur brush into contact with the charging roller 3. A fur brush made of 6-nylon, having a brush diameter of 12 mm, a filament thickness of 2 denier, a filament density of 40,000 filaments / cm ² and a brush resistance of 0.7 × 10 ⁷ Ω is used. Was set to 300 mm / sec. Other than that was carried out similarly to Example 1, and measured the density unevenness of the image and evaluated image quality. The results are shown in Table 1.

  As shown in Table 2, the image quality was good in Example 1 and Example 2, whereas the image quality was lowered in the comparative example. As a result, it has been found that by cleaning the charging roller 3 according to the present invention, foreign matter adhering to the surface of the charging roller 3 is removed, and deterioration of image quality due to charging failure can be prevented. The cleaning interval of the charging roller 3 is not particularly limited to the above embodiment, and can be set as appropriate according to the apparatus configuration and the like.

  The present invention provides a rubbing means capable of rubbing the charging means, supplies a cleaning toner from the developing device to the rotating image carrier surface during non-image formation, and the charging means from the image carrier surface. After the cleaning toner adheres substantially uniformly to the surface, a linear velocity difference is provided between the rubbing means and the charging means, and the surface of the charging means is rubbed with the cleaning toner. After the rubbing, the surface of the charging unit is cleaned by moving the cleaning toner from the surface of the charging unit to the surface of the image carrier and collecting the cleaning toner from the surface of the image carrier to the cleaning unit.

  As a result, it is possible to remove foreign matter adhering to the surface of the contact-type charging unit without using a complicated configuration, and thus it is possible to obtain stable image quality over a long period of time.

  Further, by applying a second reverse bias opposite to the charging bias to the charging unit when the toner is attached and when the charging unit is rubbed, the cleaning toner is more reliably attached to the charging unit. At the same time, the foreign matter adhering to the charging roller can be scraped off. Further, when the charging means is rubbed, a linear velocity difference is provided in the rotation direction or the axial direction of the charging means between the charging means and the contact means at the contact portion between the charging means and the rubbing means. With the configuration, foreign matters can be reliably attached to the cleaning toner, and foreign matters attached to the charging means can be removed.

  Further, by using the image bearing member as the rubbing means, it is possible to remove the foreign matter attached to the charging means with a simpler configuration. In addition, when the charging means is rubbed, by making the linear speed of the charging means larger than the linear speed of the image carrier, it is possible to improve the scraping performance of foreign matters by the cleaning toner and shorten the cleaning time. it can. Further, when the rubbing means is rubbed, the charging means reciprocates in the axial direction with respect to the image carrier, so that the foreign matters adhere to the cleaning toner more reliably and the foreign matters adhering to the charging means are removed. Can do.

  Further, when the charging unit is rubbed, the linear velocity in the rotation direction of the charging unit is made larger than the linear velocity in the rotation direction of the image carrier, whereby a simpler configuration can be achieved. Further, the rubbing means is a rubbing member that rotates in contact with the charging means, and by applying a bias having the same potential as the charging means to the rubbing member, the scraping performance of foreign matters by the cleaning toner is improved. The collection performance of the cleaning toner is also improved. In addition, the rubbing member rotates following the charging unit at least during image formation, and at the time of rubbing the charging unit, a linear speed difference is provided between the charging unit and the influence on image formation is further avoided. At the same time, the foreign matter adhering to the charging means can be efficiently removed.

  Further, when the charging means is rubbed, the foreign matter adhering to the charging means can be removed without changing the linear speed of the charging means by making the linear speed of the rubbing member larger than the linear speed of the charging means. it can. Further, when the charging unit is rubbed, the linear velocity in the rotation direction of the rubbing member can be made larger than the linear velocity in the rotation direction of the charging unit. In addition, when the charging unit is rubbed, the rubbing member reciprocates in the axial direction with respect to the charging unit, so that the foreign particles can be more reliably adhered to the cleaning toner and the foreign materials adhered to the charging unit can be removed. Can do.

  Further, when the cleaning toner is collected, the first bias applying unit applies the charging bias to the charging unit, so that the cleaning toner can be more efficiently moved from the surface of the charging unit to the surface of the image carrier. It can be done reliably.

  Further, the drive means rotates the image carrier in the direction opposite to the rotation direction when the cleaning toner is attached, and rotates in the rotation direction when the cleaning toner is collected. Recovery can be performed more reliably. In addition, by setting the interval between the developing unit and the charging unit on the surface of the image carrier to be equal to or greater than the circumferential length of the charging unit, it is possible to more reliably adhere the cleaning toner to the surface of the charging unit.

  Further, when cleaning the surface of the charging unit, the second bias applying unit applies a second reverse bias having a polarity opposite to the transfer bias to the transfer unit, so that the cleaning toner can be more reliably attached and collected. In addition, it is possible to avoid the occurrence of problems when transferring the toner image to the recording medium. Further, when the cleaning toner is adhered, the cleaning toner can be more reliably adhered from the surface of the image carrier to the surface of the charging unit by making the linear velocity of the image carrier smaller than that at the time of image formation. it can.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum (Image carrier, rubbing means)
3 Charging roller (charging means)
3a Shaft 5 Development unit (development means)
9 Cleaning device (cleaning means)
17 Transfer roller (transfer means)
21 First drive motor (drive means)
25 1st power supply (1st bias application apparatus)
27 Second power source (second bias applying device)
34 storage unit 35 control unit 41 second drive motor 51 first slide pulley 53 first guide member 55 rubbing roller (rubbing member, rubbing means)
55a Support shaft 61 Third drive motor 71 Second slide pulley 73 Second guide member

Claims (17)

An image carrier capable of rotating in a predetermined rotation direction during image formation and forming an electrostatic latent image;
Drive means for rotating the image carrier;
Contact-type charging means for charging while rotating in contact with the image carrier;
First bias applying means capable of applying a charging bias to the charging means;
Developing means for supplying toner to the surface of the image carrier and using the electrostatic latent image formed on the surface of the image carrier as a toner image;
Transfer means for transferring the toner image developed by the developing means to a recording medium;
A second bias applying unit capable of applying a transfer bias having a polarity opposite to that of the toner to the transfer unit; and a surface of the image carrier disposed upstream of the charging unit and downstream of the transfer unit with respect to the rotation direction. An image forming apparatus comprising: a cleaning unit capable of collecting the toner remaining in
A rubbing means capable of rubbing the surface of the charging means is provided,
At the time of non-image formation, the cleaning toner is supplied from the developing device to the surface of the rotating image carrier, and the cleaning toner adheres substantially uniformly from the surface of the image carrier to the surface of the charging unit. A linear velocity difference is provided between the rubbing means and the charging means, and the surface of the charging means is rubbed with the cleaning toner, and after the rubbing of the surface of the charging means, the surface of the charging means from the surface of the charging means. An image forming apparatus for cleaning the surface of the charging unit by moving the cleaning toner to the surface and collecting the cleaning toner from the surface of the image carrier to the cleaning unit.   2. The image formation according to claim 1, wherein a first reverse bias having a polarity opposite to the charging bias is applied to the charging unit when the toner is adhered and when the charging unit is rubbed. apparatus.   When the charging unit is rubbed, a linear speed difference is provided between the charging unit and the rubbing unit in the rotation direction or the axial direction of the charging unit at a contact portion between the charging unit and the rubbing unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the rubbing unit is the image carrier.   The image forming apparatus according to claim 4, wherein a linear velocity of the charging unit is greater than a linear velocity of the image carrier when the charging unit is rubbed.   6. The image forming apparatus according to claim 5, wherein when the charging unit is rubbed, the charging unit reciprocates in the axial direction with respect to the image carrier.   The image forming apparatus according to claim 5, wherein a linear velocity in a rotation direction of the charging unit is greater than a linear velocity in a rotation direction of the image carrier when the charging unit is rubbed.   The image according to claim 3, wherein the rubbing unit is a rubbing member that rotates in contact with the charging unit, and a bias having the same potential as that of the charging unit is applied to the rubbing member. Forming equipment.   9. The rubbing member rotates at least following the charging unit during image formation, and a linear velocity difference is provided between the rubbing member and the charging unit during rubbing of the charging unit. The image forming apparatus described.   The image forming apparatus according to claim 9, wherein when the charging unit is rubbed, a linear velocity of the rubbing member is larger than a linear velocity of the charging unit.   The image forming apparatus according to claim 10, wherein a linear velocity in a rotation direction of the rubbing member is larger than a linear velocity in a rotation direction of the charging device when the charging device is rubbed.   The image forming apparatus according to claim 10, wherein the rubbing member reciprocates in the axial direction with respect to the charging unit when the charging unit is rubbed.   The image forming apparatus according to claim 1, wherein when the cleaning toner is collected, the first bias applying unit applies the charging bias to the charging unit.   The drive means rotates the image carrier in the direction opposite to the rotation direction when the cleaning toner is attached, and the rotation direction when the charging means rubs and collects the cleaning toner. The image forming apparatus according to claim 1, wherein the image forming apparatus is rotated.   The image forming apparatus according to claim 1, wherein an interval between the developing unit and the charging unit on the surface of the image carrier is equal to or greater than a circumferential length of the charging unit.   16. When cleaning the surface of the charging unit, the second bias applying unit applies a second reverse bias having a polarity opposite to the transfer bias to the transfer unit. An image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein when the cleaning toner is attached, a linear velocity of the image carrier is lower than that during the image formation.

Images